A fear of disease-causing "miasmas" from rotting corpses lead to
designating new cemeteries on the outskirts of Paris, in the fashion of
the Greeks and Romans. These include Pere Lachaise. The fear of the
stench from the mass grave of Saints Innocents lead to the removal of
human remains and was performed on winter nights over a two year
period, from 1785-1787. These bones were placed in the Catacombes
--named after the Roman catacombs, though these were simply
abandoned quarries once populated by thieves--and were sorted and
stacked neatly by type, just like in the Imperial City. The transfer of
other urban cemeteries to the Catacombes occured until the 1870s;
it currently hold the remains of six million Parisians. The Catacombs
became a popular novelty for the old nobility who held dinner parties
and picnics there.

In 1864, Haussmann and his team of engineers decided the best
solution for the overcrowded cemeteries was mechanical: to develop
one large cemetery for all of Paris at Mery-sur-Oise connected by a
special railway. This funerary line would connect to the three other
principal, overcrowded cemeteries: Napoleon I's Montmartre, Pere
Lachaise and Montparnasse. As Saalman puts it, "Insensitive to
the negative psychological overtones of his 'iron horse express to the
grave' conception, Haussmann found himself unprepared for the
popular outcry his proposal raised, and nothing became of it."

Nadar's photo-recreation of the emptying of urban cemetaries, 1861.
The exposure required 20 minutes due to the lighting conditions
so a mannequinwas used.